The LTPS adopts polycrystalline silicon to manufacture TFT. As compared with the production of amorphous silicon TFT, LTPS TFT has higher electron mobility. LTPS TFT can be applied to the production of liquid crystal display having a higher resolution and low power consumption. Thus, low-temperature polysilicon technology has been widely adopted and developed.
Lightly Doped Drain (LDD) relates to arrange a lightly doped area within a trench of the TFT, and the lightly doped area is close to the drain. This may decrease the peak electrical field in a rim of the drain so as to suppress heat electron effect. Currently, when the LTPS technology is adopted in LDD manufacturing process, the mask process has to be performed twice, respectively during heavy and light doped processes in source and drain. Not only the cost is high, but also the manufacturing period is long.